PyErr_Display(), PyErr_WriteUnraisable(): Coverity found a cut-and-paste

bug in both:  `className` was referenced before being checked for NULL.

Python/errors.c

@@ -588,13 +588,16 @@ PyErr_WriteUnraisable(PyObject *obj)
 	if (f != NULL) {
 		PyFile_WriteString("Exception ", f);
 		if (t) {
-			char* className = PyExceptionClass_Name(t);
 			PyObject* moduleName;
+			char* className = PyExceptionClass_Name(t);
+
+			if (className != NULL) {
 				char *dot = strrchr(className, '.');
 				if (dot != NULL)
 					className = dot+1;
-			moduleName = PyObject_GetAttrString(t, "__module__");
+			}
 
+			moduleName = PyObject_GetAttrString(t, "__module__");
 			if (moduleName == NULL)
 				PyFile_WriteString("<unknown>", f);
 			else {

Python/pythonrun.c

@@ -1132,13 +1132,15 @@ PyErr_Display(PyObject *exception, PyObject *value, PyObject *tb)
 			/* Don't do anything else */
 		}
 		else if (PyExceptionClass_Check(exception)) {
+			PyObject* moduleName;
 			char* className = PyExceptionClass_Name(exception);
+			if (className != NULL) {
 				char *dot = strrchr(className, '.');
-			PyObject* moduleName;
 				if (dot != NULL)
 					className = dot+1;
-			moduleName = PyObject_GetAttrString(exception, "__module__");
+			}
 
+			moduleName = PyObject_GetAttrString(exception, "__module__");
 			if (moduleName == NULL)
 				err = PyFile_WriteString("<unknown>", f);
 			else {